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As someone who's been working on figuring out a way to transpile or interpret a powerful dynamic language to Lua, JavaScript, Python and Go, the really tough th

by wtbob 11y ago

As someone who's been working on figuring out a way to transpile or interpret a powerful dynamic language to Lua, JavaScript, Python and Go, the really tough thing to do is non-local exits. If you can solve that, I think that everything else is easy (well, a Simple Matter of Programming anyway). It's okay if your target language already supports non-local exits, particularly parameterised ones (although even that can be faked with a well-designed global), but if it doesn't then it's a pain (imagine how you'd do it in Go: every single function call will return an additional value, indicating if a non-local exit is intended). Alternatively, imagine trying to transpile call/cc to JavaScript…

PeCaN 11y ago
Just transform it to continuation-passing style[1] and call/cc is no problem (neither are non-local exits). Granted your compiled code will be somewhat large and not much like 'regular' code in the language. That can be solved by doing selective CPS transform (IcedCoffeeScript[2] does this), but that gets slightly less straightforward. Compiling continuations to a dynamic language is actually really easy. -- 1: https://en.wikipedia.org/wiki/Continuation-passing_style https://en.wikipedia.org/wiki/Continuation-passing_style 2: http://maxtaco.github.io/coffee-script/ http://maxtaco.github.io/coffee-script/
- truncate 11y ago
  I'm interested to know more about IcdeCoffeeScript approach. Any blogs/articles that you know of? Typically direct CPS conversion are straightforward, but the performance suffers a lot. I'm looking for languages that are using some hybrid approaches.
- wtbob 11y ago
  > Just transform it to continuation-passing style and call/cc is no problem (neither are non-local exits). Granted your compiled code will be somewhat large I'm well aware, but CPS code can be _insanely_ large (essentially a function declaration for every line of code in the original source). That's quite painful.
meric 11y ago
Does Javascript's try...catch and error count as non-local exit?

by wtbob 11y ago

PeCaN 11y ago

Just transform it to continuation-passing style[1] and call/cc is no problem (neither are non-local exits). Granted your compiled code will be somewhat large and not much like 'regular' code in the language. That can be solved by doing selective CPS transform (IcedCoffeeScript[2] does this), but that gets slightly less straightforward. Compiling continuations to a dynamic language is actually really easy. -- 1: https://en.wikipedia.org/wiki/Continuation-passing_style https://en.wikipedia.org/wiki/Continuation-passing_style 2: http://maxtaco.github.io/coffee-script/ http://maxtaco.github.io/coffee-script/

truncate 11y ago
I'm interested to know more about IcdeCoffeeScript approach. Any blogs/articles that you know of? Typically direct CPS conversion are straightforward, but the performance suffers a lot. I'm looking for languages that are using some hybrid approaches.
wtbob 11y ago
> Just transform it to continuation-passing style and call/cc is no problem (neither are non-local exits). Granted your compiled code will be somewhat large I'm well aware, but CPS code can be _insanely_ large (essentially a function declaration for every line of code in the original source). That's quite painful.

meric 11y ago

Does Javascript's try...catch and error count as non-local exit?